need to modify existing Esp8266 Webserver

I am using Esp8266 + Ultrasonic sensor as water tank controller. There is a webserver, which shows the level of water in % and also there is ON/OFF slide switch, which controls the relay. I need to add some settings for user in webserver like 1) Timer Clock through which user set time and relay trigged on given time, 2) enable/disable check box for timer, 3. enable user to set the height of tank manually, 4. if tank is 50% then motor should not run more than 20 minutes (to avoid dry-run).